We're All New Orleanians Now

Jim Titus, chief sea-level-rise expert at the Environmental Protection Agency (EPA), estimates that shore protection for the lower 48 states could cost around $1 trillion. And seawallsa necessity to protect places like Manhattancould create as many problems as they solve. Dikes, levees, and bulkheads will destroy many coastal wetlands by preventing them from migrating inland as the seas advance.

Most of the coastal wetlands in the mid-Atlantic could disappear by the end of the century if they have no place to go and the seas rise three feet or more. These wetlands are highly valuable, reducing the impact of floods, protecting against storms, and shielding freshwater supplies from the ocean. They’re also key nurseries for fish: About two-thirds of the commercial fisheries off the Atlantic depend on wetlands, where invertebrates and small fish that feed on decomposing matter support rockfish, menhaden, blue crab, and other large species.